This invention relates to a linear photo sensing device including a first electrode section with discrete multi-channel electrodes linearly arrayed, a linear electrode section, and a photo-electric converting semiconductor layer sandwiched between those electrode sections.
The linear photo sensing device is used with an X-ray radiography system of the type in which an imaging plate as a stimulable phosphor plate, for example, is used. The device reads out the X-ray image data as stored in the imaging plate in the form of latent image.
An accelerated phosphorescence detector is structured as shown in FIG. 1. As shown, imaging plate 1 is placed between stimulating ray source 2 and linear photo sensing device 3, which are oppositely disposed, and is movable in the Y direction. One of the major surfaces, which is denoted as la, and stores the radiation energy as a latent image, is irradiated with the stimulating rays, usually laser beams, emitted from stimulating ray source 2. Upon the irradiation, the accelerated phosphorescence is emitted from the other major surface 1 of imaging plate 1, and is sensed by linear photo sensing device 3. The stimulating rays and linear photo sensing device 3 cooperate to scan imaging plate in the X direction. The relative movement of simulating ray source 2 and linear photo sensing device 3, to imaging plate 1 makes the scanning in the Y direction. The light beam sensed by linear photo sensing device 3 is converted into the electrical signal, and processed into the image data corresponding to the latent image, stored, and displayed or recorded in a film (e.g., a photographing film or an X-ray film).
Specifically, the size of imaging plate 1 is 400mm.times.400mm, and the optical image data as collected by linear photo sensing device 3 is processed into the electrical image data of 2,000.times.2,000 pixels (picture elements). The pixels of "n", Px1, Px2, Px3,... Pxn which are linearly arrayed in the X direction as shown in FIG. 2, are substantially simultaneously read out through the scanning of it by the combination of stimulating ray source 2 and linear photo sensing device 3. Then, the combination of the light source 2 and the sensing device 3, and imaging plate 1 are successively shifted "n" times in the Y direction orthogonal to the X direction, to scan all of the pixels. To obtain the image data of 2,000.times.2,000 pixels, n=2,000.
Linear photo sensing device 3 is disposed facing stimulating ray source 2. Structurally, the device 3 contains sensing elements E1, E2, E3,... En (n=2,000) of 2,000 channels, which correspond to 2,000 pixels as the total number of pixels of one linear scanning of X direction on image plate 1. This is clearly illustrated in FIG. 3. The surface 1a of imaging plate 1 is irradiated with the linear stimulating rays, and the surface 1b emits rays of light. The emitted rays are sensed and detected by linear photo sensing device 3, with the resolution of 2,000 pixels.
In the relative movement of the light source 2 and the sensing device 3 to imaging plate 1, the light source 2 and linear photo, sensing device 3 are fixed together, and imaging plate 1 is moved in the direction Y.
The linear photo sensing device 3 shown in FIG. 3 is composed of first electrode 5, amorphous silicon layer 6, and second electrode 7. The first electrode 5 includes electrode elements 5(1), 5(2), 5(3),... 5(n) (n=2,000), a semiconductor layer 6 with the photoelectric converting function covering the surface of first electrode 5, such as amorphous silicon, and a second electrode 7 as a transparent conductive layer and covering the surface of amorphous silicon 6.
The length L of the sensing device 3 is 400mm, corresponding to the X-directional length of imaging plate 1. The size of each electrode element of first electrode 5 is determined allowing for these figures of 400mm and 2,000 pixels. For example, the pitch P of each electrode element is 180 .mu.m, and the length S of each electrode element is 120 .mu.m. Hence, the electrode element interval is 60 .mu.m.
The light rays emitted from the surface 1b of imaging plate 1 are applied to the second electrode 7, and are converted into the corresponding electrical current signal by amorphous silicon layer 6. The signal current is output to first electrode section 5 right under the light irradiation location. In this way, the image light rays emitted from the surface la of imaging plate 1 are sensed and detected.
With the structure of electrode elements arrayed at 60 .mu.m intervals, the current which should be directed to the intended element may flow into the elements adjacent to the intended element, via amorphous silicon 6. This results in the cross talk of the detected signal.
To cope with this problem, it is ideal that first electrode 5, amorphous silicon layer 6, and second electrode 7 are separately formed, to form separate sensing elements of 2,000 channels, as shown in FIG. 4. At the present stage of the photolithography technology, it is very difficult to make the patterning of three layers with satisfactorily high accuracy in the order of 10 .mu.m. Particularly the aligning of the mask of each layer is very difficult. Therefore, it is almost impossible to manufacture the linear photo sensing device as shown in FIG. 4.